I have seen these cracked in half on a customers car, probably from overtightening wheels or rust on the hubs/wheels, the customer was fine with it so, back on the cracked spacer went. For the record, his wheels are still on as far as I know, he hasn't been back. About the grinding of the clappers, we did it to fit late model Chevy Malibu wheels on a mid '90s lumina, it worked fine, it just depends how much metal is there to work with.